1. Field of the Invention
The invention relates to an electric contact-maker apparatus having, on the one hand, a housing of general prismatic shape with a rectangular base, adapted for receiving an electromagnet and which comprises side walls matching the contour thereof while leaving two external cavities in the vicinity of parallel edges and, on the other hand, a removable electric module whose case is associated with the housing and two electric connection pieces of which are connected respectively to two terminals for the external connection of the coil of this electromagnet.
2. Description of the Prior Art
Such apparatus, which have the property of providing, for example, protection of the coil against voltage surges appearing at its terminals by means of an RC network, also benefit from a substantial reduction of the level of the parasites which accompany energization and/or deenergization of this coil; in this connection their use is either recommended or prescribed when electronic apparatus sensitive to such parasites are in the immediate vicinity of or are exposed to radiation emitted by conductors passing close by.
The user, who must take the above-mentioned precautions, generally meets modules which may be associated with a standard contact-maker by being clamped thereto, either on the front portion of a part of the housing, or else placed between the base of the housing and a plate intended for fixing same.
In the first case, the volume occupied by this module reduces that which may be used for positioning auxiliary contact blocks which are generally secured to this same front face.
In the second case, the need to dispose such a protection module, subsequently, requires removal of the contact-maker for disengaging it from its fixing plate; this operation generally results in a loss of time to the extent that the bundles of conductors connected to the different terminals of the contact-maker make it difficult to have access to the fixing screws or, respectively, to the hook for hooking it on to a standardized shaped rail.
In another approach, known for example from the patent EP 198 099, the housing of the protection module is removably housed in a compartment opening on to a side face of the contact-maker, and the necessary electric connections are provided by resilient lugs applied on conducting pieces which extend between the terminals for connection of the coil and other resilient pieces which are fast with the carcase of this coil.
Apart from the disadvantages due to the need to manufacture and fit these additional conducting pieces, such an arrangement may be further reproached with the resulting impossibility of positioning such a module when required after a multiplicity of contact-makers have been fitted and fixed against each other; the only approach permitting such positioning would be to systematically leave, between two adjacent contact-makers, a gap greater than the thickness of the case of the module : finally, the adjacent side faces of two contact-maker apparatus are those which are generally chosen for receiving a reciprocal locking device when two adjacent contact-makers are associated in a change-over circuit, so that trouble-shooting at this position could also require dismantling of this device.
A protected contact-maker is also known, for example from the model of utility DE 82 36 682, in which the presence of a clearance in the housing of this contactmaker is used for housing a protection module; the fact that the electric connection and subsequent positioning of this module require loosening of the connection terminals of the coil, may be felt as a hindrance or a risk when these terminals are not adjacent for, on the one hand, the simultaneous insertion of two conductors or more in a connection terminal is never easy whereas, on the other hand, mechanical holding of the module in position may in the long run result in exaggerated fatigue of the single connection lug serving for this purpose.